Under each key of the piano is a switch that allows the circuit to identify when a key is pressed. We will keep an LED in the circuit to light up as an indicator that the key press has been recognized. Then the output of the key press will go to a series of relays that will trigger the solenoid valves.
a schematic of the key action
hooking up the circuit
the relays soldered to a perf board
Here is a video of us testing our circuit with the solenoid valve: